load balancing in interaction with handover...

FP7 ICT-SOCRATES

Load balancing in interaction with handover

optimisationp

Presented by Andreas LobingerNokia Siemens Networks

FP7 SOCRATES final workshopKarlsruhe, Germany

22 F b 201122 February 2011

Contributors: Irina Balan (IBBT), Thomas Jansen (TU BS), Szymon Stefanski (NSN)

Outline

Overview on Load Balancing (LB)(Deliverable 5.9: section 8.4)

Overview on Handover Parameter Optimization (HPO) Overview on Handover Parameter Optimization (HPO) (Deliverable 5.9: section 8.3)

LB + HPO integration, problem description LB + HPO, coordination approach

(D li bl 5 9 ti 9 1)(Deliverable 5.9: section 9.1)

Conclusions and future work

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Andreas Lobinger, Nokia Siemens Networks, CTO Research

Load Balancing (LB)

General Idea: Shift load of a overloaded cell by forced handovers to surrounding low loaded cells t d i h i th l d diti f t k so act on dynamic changes in the load conditions of a network self optimisation.

SeNB TeNB

Control paramters:– Cell Individual Offsets for HO

What is load?

SeNB TeNB

Hysteresis h2

What is overload?y

Di t

LB HO offset

Hysteresish1

Distance

SeNB TeNB

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LB, example result

Typical simulation scenarios contain an area of high load and some dynamic changes ( here moving the hotspot)

180

200

scenario 3

referencewith load balancing

1500

2000

2325

non-regular network; hotspot is moving from cell 27 to 13

Base Stationshotspot route

140

160

180

n ne

twor

k

500

1000

1500

4 5

81920

2223

24

2526

27

28

80

100

120104

atis

fied

user

s in

-500

0 1 2

3

6 78

9

101116

17

21

2829

30

[]

20

40

60

35

n un

sa

-1500

-100012 1314

15

18

3132

333435

0 200 400 600 800 1000 1200 1400 1600 18000

20

t [s]

-2000 -1500 -1000 -500 0 500 1000 1500

-2000 3336

X [m]

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General idea: Gather information in the network about mobility

Handover Parameter Optimization (HPO)

General idea: Gather information in the network about mobility problems and control the handover parameters to reduce them. generate reasonable parameters for decent network performanceg p p Information as KPI (key performance indicators) of typical handover

problems – Radio Link Failure– Handover Failure

Pi P h d– Ping-Pong handover Parameters controlled

Hysteresis– Hysteresis– Time To Trigger

The effect of HO parameterpchanges


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HPO, example results

Simulation scenarios: Regular Networks, all users the same speed

60

70

Handover failure ratioPingPong handover ratioRadio link failure ratio

1

ndov

er ra

tio

40

50

o [%

]

8

10

12

50

0.5

ing-

Pong

han

20

30

HPI

ratio

2

4

6

8

0.1

0.250.5

1

Hysteresis [dB]Time-to-Trigger [s]

P

100 200 300 400 500 600 700 800 900 10000

10

Hysteresis [dB]Time to Trigger [s] 100 200 300 400 500 600 700 800 900 1000Simulation Time [s]


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Approach: Run both algorithms in parallel and use a coordinator to

Integrated Use Case, LB + HPO

Approach: Run both algorithms in parallel and use a coordinator to limit the controls of the system. Note: Both algorithms use the HO decisiong

Interaction example:e ac o e a p e• Overload in SeNB shifts cell

border to point 2• Some user in the area

between point 1 and 2 will be handovered to TeNB ig

nal s

treng

th

handovered to TeNB• Increase of the Hysteresis in

TeNB can then shift the borderR

ecei

ved

s

TeNB can then shift the border to point 3 and increase the load in SeNB again


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Integrated Use Case, LB + HPO

Coordinator approach following th f k f ththe framework of the SONcoordinator

– Coordination withCoordination with higher priority for HPO (COO1)C di ti ith– Coordination with higher priority for Load Balancing (COO2)

– Coordination mechanism to

mechanism to avoid abnormal situations (COO3)


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Integrated Use Case LB + HPO, example results25

referenceHPO

6Ping-Pong Handover Ratio

15

20

ers

HPOLBLB + HPOLB + HPO + COO

2

4

[%]

10

15

Uns

atis

fied

Use

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Handover Failure Ratio

5

2

3

4

[%]

0 200 400 600 800 1000 12000

t [s]

0 200 400 600 800 1000 12000

1

35

40unsatisfied usersHPIping pong

3

4

RLF Ratio

25

30

alue

ping-pong

HPIHO-failure

HPIRadio Link Failure

0 200 400 600 800 1000 12000

1

2

3

[%]

10

15

20

KP

I va

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0 200 400 600 800 1000 1200t [s]

reference HPO LB HPO + LB COO0

5

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Conclusion and Outlook

In the HPO and LB use cases dedicated optimization algorithms were designed. Just putting them together can lead to additional old or new

problems. With a coordinator giving priority to one or the other algorithm With a coordinator giving priority to one or the other algorithm

already some problems can be resolved. A full coordinator also looking at interaction or abnormal behaviourA full coordinator also looking at interaction or abnormal behaviour

can lead to reasonable system performance.

Integration does not stop here … Still the details of a coordinator role or network function is ffs in

3GPP


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Thank you.


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